1. Field of the Invention
The present invention relates to a connector, and particularly to a ball grid array socket connector used to electrically connecting an integrated circuit (IC) package assembly to a PC board.
2. Description of the Related Art
Ball Grid array (BGA) socket connectors are widely used for electrically connecting an integrated circuit (IC) package to a PC board. A typical BGA socket connector includes a number of solder balls each of which is attached to a tail of a corresponding conductive contact before the connector is mounted onto a PC board. So, during the mount of the connector onto the PC board, the solder balls are heated to about 220xcx9c230xc2x0 C. and become soft or melting and electrically interconnect the conductive contacts with solder pads on the PC board after they are refrigerated. The BGA socket connector has several advantages over other connectors. One obvious advantage is that there are no leads that may be easily damaged during handling. Another advantage is that the solder balls are self-centering on die pads and can be easily attached to the tails of the conductive contacts. Still other advantages include smaller size, fine pitch, high density, better electrical performances, better package yields, and so on.
However, problems can accrue with respect to the mount of the connector onto the PC board. First, the size of the balls should be strictly controlled. If the solder balls are too small, some of the conductive contacts may not be reliably connected to the solder pads on the PC board, therefore open circuits happen. If the solder balls are too large, the redundant solder may bridge with neighbor solder balls, therefore short circuits happen. Second, the solder balls may be collapsed by the weight of the connector and the IC package assembly during the mount. Third, heat may accumulate around the solder balls and is not easily dissipated. The present invention is aimed to address the above issues.
An object of the present invention is to provide a ball grid array socket connector that can be reliably mounted onto a PC board.
To obtain the above object, a ball grid array socket connector includes an insulative base, a number of conductive contacts fixed to the base, a number of solder balls attached to tail portions of corresponding contacts and a cover movably attached to the base. The base has a top surface, a bottom surface and defines a number of cavities through the top surface and the bottom surface. The cavities are arranged in a matrix. The contacts are, received in corresponding cavities of the base. The base provides a number of stand-offs which downwardly protrude from the bottom surface of the base and terminate at a plane generally parallel with the bottom surface of the base. The solder balls each have a bottom tip that downwardly extends beyond the plane that the stand-offs terminate at. The base defines a number of notches in the bottom surface thereof. The notches locate at outer sides of the matrix of cavities.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description of the present embodiment when taken in conjunction with the accompanying drawings.